The leading edge of the semiconductor processing industry is currently advancing production to the 65 nanometer and 45 nanometer nodes. Further, development is currently underway at the 32 nanometer and 22 nanometer nodes. Accordingly, it is increasingly critical that semiconductor processing tools and the processing itself be controlled to tolerances and conditions never previously required. The cost of wafer scrap and maintenance downtime continues to drive the desire to control processes and equipment to tighter levels, and as other problems arise that were insignificant to processes above 100 nanometers, process and equipment engineers look for new and innovative ways to better control semiconductor processing.
During the manufacture of semiconductor wafers, there are multiple tools and process steps to which a wafer is exposed. During each of these steps there are potential defects that may be caused by dirty equipment and/or poor process conditions that can cause degradation in yield of the final integrated circuit devices due to microscopic particles being deposited on the wafer's surface. Thus, it is critical to keep all process stages and steps as clean as reasonably possible and to be able to monitor the condition of these various stages before committing wafers to the process. This is important because each wafer may contain the circuitry for tens or even hundreds of integrated circuit devices, and a single lost wafer may result in hundreds or thousands of dollars worth of scrap.
Traditionally, wafers are test-run through the semiconductor processing tool and particles on the wafer are counted both before and after the test run. The difference in the number of particles is then attributed to the tool. This is a time-consuming process and may not provide any indication of where, within the tool, the particles were deposited. Accordingly, if too many particles are found on a given test run wafer, it simply indicates that the semiconductor processing tool is too dirty and that further technician efforts are required to open the tool, identify the source(s) of particles, and generate appropriate corrective action. Once this process is complete, the wafer must be test run again and the entire process repeated until there is simply an indication that the semiconductor processing tool is suitably clean.